Digitizer sensors are used for touch detection in many Human Interface Devices (HID) such as laptops, track-pads, MP3 players, computer monitors, and smart-phones. Capacitive sensors are one type of digitizer sensors. The capacitive sensor senses positioning and proximity of a conductive object such as a conductive stylus or finger used to interact with the HID. The capacitive sensor is often integrated with an electronic display to form a touch-screen. Capacitive sensors include antennas or lines constructed from different media, such as copper, Indium Tin Oxide (ITO) and printed ink. ITO is typically used to achieve transparency. Some capacitive sensors are grid based and operate to detect either mutual capacitance between electrodes at different junctions in the grid or to detect self-capacitance at lines of the grid.
Signal emitting styluses, e.g. active styluses, are known in the art for use with a digitizer system. Position of the stylus is tracked by picking on a signal emitted by the stylus with the digitizer sensor. Some active styluses emit a signal that includes information. The information may be pressure applied on the writing tip as sensed by a pressure sensor integrated on the stylus. The digitizer system decodes the information and reports the pressure or the tip status as one of touch and hover based on the decoded information.